Monitoring the state of a communications network

ABSTRACT

An interface element is adapted to interface with a communications network and includes a monitor to monitor the state of the network, and a method of using the interface element. The monitor may monitor the state of the network by monitoring the state of a link or component of the network, by receiving one or more messages regarding the state of the link/component. The monitor may monitor the state of the network by registering any changes in the state of the network or by registering any faults occurring in the network. The monitor may communicate the state of the network to one or more components of the network. The interface element may react to the state/changes in the state of the network. The monitor may comprise a router, running routing protocol software with which the network can communicate, e.g., the Open Shortest Path First routing protocol. The interface element may comprise a host, such as a residential gateway programmable device. The communications network may be a packet-switched internet protocol based network and may carry telephony-type information and data information.

This invention relates to monitoring the state of a communicationsnetwork, and particularly monitoring changes in the state of a network,for example due to faults occurring in the network, both locally to aninterface element of the network and farther into the network.

Communications networks having numerous topologies exist. As suchnetworks become larger and more complex, it is often desirable tomonitor the state of a network and particularly any changes therein. Forexample, if a fault should occur on any link in a network, it isdesirable that this change in the network state should be detectedrapidly such that, for example, appropriate action can be taken.

Monitoring and being able to react to changes in the state of a networkare particularly important when packet-switched communications networksare used to carry telephony-type information, e.g. voice or videoinformation. Traditionally, such information has been carried bycircuit-switched communications networks, i.e. networks whereeffectively a dedicated connection is established between a sender and areceiver of the information. With the advent of more and more dataapplications, communications networks have been developed to carry datainformation, e.g. data files, e mails, etc. Such networks includepacket-switched networks, i.e. networks in which information to becarried is split up into packets, which may take different routes acrossa network from a sender to a receiver. This way of carrying informationoffers various advantages, e.g. the ability to more easily accommodateadditional users, and such networks are now being used for carryingtelephony-type information. When information is carried in packets, itis possible that one or more packets may be delayed or lost, e.g. due toa fault occurring in the communications network. This is not so criticalfor data information, where delayed packets can be reintroduced into thedata stream in the correct place and lost packets can be retransmitted.However, for telephony-type information, delays exceeding a fewmilliseconds and retransmission are undesirable if, for example, a callin progress is not to be interrupted, and an acceptable grade ofservice, e.g. a ‘Five Nines’ telco-grade, is to be provided. To usecommunications networks such as packet-switched networks for carryingtelephony-type information, it is desirable that any changes in thestate of any part of the network, e.g. due to faults, be monitoredpreferably rapidly, so that action, e.g. rerouting, can be taken withoutundue delay or loss of information. It is desirable that components of anetwork and elements which interface with the network are capable ofmonitoring or are informed of the state of the network, to allow them tocompensate for any changes therein.

Systems for monitoring the state of a communications network are known.For example, the state can be monitored by means of timeouts betweencomponents of the network or between elements which interface with thenetwork. However, these by their very nature take time to expireproviding a slow detection of faults and increasing the possibility ofunacceptable delays or loss of information. Faster detection of faultscan be achieved by providing intelligent monitoring devices within thenetwork. However this approach suffers from the addition of, oftenexpensive, equipment to the network, which requires access to andmodification of the network, and provides an additional possible sourceof faults within the network.

According to a first aspect of the present invention there is providedan interface element adapted to interface with a communications network,the element comprising monitor means to monitor the state of thenetwork.

According to a second aspect of the present invention there is provideda method of using an interface element according to the first aspect ofthe invention to monitor the state of a communications network.

The monitor means may monitor the state of the network by receiving oneor more messages regarding the state of at least one link of thenetwork. The or each message may comprise information regarding theability of the link to carry information. The or each message may bereceived from one or more link-state monitors of the interface element.The or each message may be received from one or more components of thenetwork. The link may comprise, for example, a peripheral link of thenetwork, which may connect the network and the interface element.

The monitor means may monitor the state of the network by receiving oneor more messages regarding the state of at least one component of thenetwork. The or each message may comprise information regarding theability of the component to carry information. The or each message maybe received from the component.

The monitor means may monitor the state of the network by receiving oneor more massages regarding one or more connection paths available to oneor more components of the network. The or each message may compriseinformation regarding connection paths between, for example, the or eachcomponent and one or more other components of the network and/or one ormore elements which interface with the network. The or each message maycomprise information regarding a measure of the cost of using the oreach connection path. The or each message may be received from the oneor more

The monitor means may monitor the state of the network by registeringany changes in the state of the network, for example changes in thestate of at least one link or component of the network. The monitormeans may register any changes in the ability of a link or component ofthe network to carry information. A change in the state of the networkmay be caused by a fault occurring in the network. The monitor means maymonitor the state of the network by registering any faults occurring inthe network, for example faults occurring in a link or a component ofthe network.

The monitor means may communicate with one or more components of thenetwork. For example, the monitor means may communicate the state of thenetwork and/or changes in the state of the network to the one or morecomponents of the network. This may comprise communicating one or moremessages regarding the state of at least one link and/or at least onecomponent of the network to the one or more components of the network.Communicating with the one or more components may allow the network tocompensate for any changes occurring in the state of the network. Themonitor means may communicate the state of the interface element and/orchanges in the state of the interface element to one or more componentsof the network.

Monitoring the state of the network may allow the interface element toreact to the state of the network. Monitoring any changes in the stateof the network, e.g. due to a fault, may allow the interface element tocompensate for a change in the state. The interface element and thenetwork are therefore said to be more resilient. The interface elementmay compensate for a change in the state of the network by causinginformation sent by it to the network to be rerouted. Because themonitor means actively registers state changes and does not rely ontimeouts, the rerouting can take place very quickly. Rerouting of theinformation preferably takes place in sub-second times. The network cantherefore more easily provide a required level of service for handlingtelephony-type information. The monitor means may provide a routingfunction.

By providing the interface element with the means to monitor the stateof the network, this avoids providing additional components to thenetwork or modification of existing components of the network to carryout this function. This reduces the expense involved in developing thenetwork, access required to the network, and avoids adding additionalpossible sources of faults within the network.

The monitor means may be implemented on one or more microprocessors,which may be added to the interface element. The monitor means may beimplemented on one or more existing microprocessors of the interfaceelement. The monitor means may comprise a router. The router maycomprise one or more microprocessors which are added to the interfaceelement, or which are existing microprocessors of the interface element.The router may comprise one or more microprocessors running routingprotocol software. The routing protocol software preferably comprisesrouting protocol software with which one or more components of thenetwork can communicate. This will allow information on the state of thenetwork and/or the state of the interface element to be communicatedbetween the router and the network. The routing protocol softwarepreferably comprises a standard protocol implemented on one or morecomponents of the network, e.g. the Open Shortest Path First (OSPF)routing protocol. Using a standard routing protocol allows the monitormeans to be readily used with a network which can communicate with thisprotocol. The monitor means preferably connects the interface element tothe communications network. The monitor means may comprise two or moreconnections to the communications network.

The interface element may comprise a host, for example a telephone or apersonal computer, or a media gateway programmable device or aresidential gateway programmable device. The interface element may runapplication software, used in the operation of the element. Theapplication software is preferably implemented in the interface elementseparately from any routing protocol software of the monitor means. Theinterface element may comprise one or more microprocessors runningapplication software. The interface element may comprise one or moremicroprocessors running communications stack software. The interfaceelement may comprise one or more link-state monitors. The or eachlink-state monitor may be connected between the monitor means and thecommunications network.

The communications network is preferably a packet-switched network. Thecommunications network may be an internet protocol (IP) based networkoperating over a link-layer protocol, e.g. an Ethernet network or aPacket over SONET/SDH network or a Packet over ATM AAL5 network or aPacket over ATM AAL2 network. The communications network may carrytelephony-type information, e.g. voice or video information, and/or datainformation, e.g. data files or e mail.

An embodiment of the invention will now be described by way of exampleonly, with reference to the accompanying drawings in which:

FIG. 1 is a schematic representation of an interface element accordingto the first aspect of the invention, and

FIG. 2 is a schematic representation of a communications networkconnected to the interface element of FIG. 1.

Referring to FIG. 1, the interface element 1 comprises a microprocessor2 running application software, a microprocessor 3 runningcommunications stack software, monitor means comprising a router 4 andlink-state monitors 5 and 6. The interface element is connected to anumber of telephones (not shown). The microprocessor 2 is connected tothe microprocessor 3, which is connected to the router 4, which in turnis connected to the link-state monitors 5, 6, as shown. The link-statemonitor 5 is connected to link L1 of a communications network 7, and thelink-state monitor 6 is connected to link L2 of the communicationsnetwork 7. The network is a packet-switched network using the OSPFrouting protocol. The application software running on microprocessor 2enables the interface element to receive information from the telephonesand to packetise the information. The information packets are thenpassed to the microprocessor 3 running the communications stack softwarewhich decides on the way in which the packets are to be sent to thecommunications network 7. The packets are forwarded to the router 4 andfrom there to the link-state monitors 5, 6 for onward transmission tothe network 7 via link L1 and/or link L2. In a similar fashion,information packets from the network 7 are received by the link-statemonitors 5, 6 via link L1 and/or link L2, and are transmitted to therouter 4, the microprocessor 3, and onwards to the microprocessor 2where the packets are reassembled and the information transmitted to thetelephones as appropriate. In addition to carrying information packetsto and from the interface element, the links L1 and L2, when operatingnormally, also send a background pulsed signal to the link-statemonitors 5, 6. On receipt of this signal each monitor sends messages tothe router 4 indicating that the links are able to carry information.

The router 4 comprises a microprocessor which runs the OSPF routingprotocol. The router microprocessor monitors the state of the network 7,by receiving messages regarding the state of the links L1 and L2 fromthe link-state monitors 5, 6, and by receiving messages regarding thestate of the components of the network and regarding the connectionpaths available to the components via the links L1 and L2. The routermicroprocessor also sends messages regarding the state of the networkand the state of the interlace element to the network components, sothat they may compensate for any changes therein.

FIG. 2 illustrates a communications network connected to the interfaceelement 1 of FIG. 1. The network comprises a first switch 10, a secondswitch 11, a first router 12 and a second router 13. The first switch 10is connected to the interface element via the link L1, and the secondswitch 11 is connected to the interface element via the link L2. Thefirst switch 10 is connected to the first router 12 via a link L3, andthe second switch 11 is connected to the second router 13 via a link L4.The first router 12 is connected to a host 14 via a link L5, and thesecond router 13 is connected to the host 14 via a link L6. In normaloperation information packets from the interface element 1 are sent tothe host 14 via link L1, first switch 10, link L3, first router 12 andlink L5 and/or via link L2, second switch 11, link L4, second router 13and link L6. However, circumstances may occur in which, for example,link L1 becomes unable to carry information packets, for example a faultmay occur on this link. In such a case, the link-state monitor 5 sends amessage to the router 4 indicating that the link L1 cannot carryinformation, and the router 4 reroutes all the information packets vialink L2. The router 4 also communicates the change in the state of linkL1 to the components of the network via link L2. This allows the networkto reroute all the information for the interface element 1 via link L2.This is an important function of the router 4 as generally the switches10, 11 are relatively dumb and cannot communicate such a state change tothe other components of the network, to allow such rerouting.

1-38. (canceled) 39: An interface element for interfacing with acommunications network having network elements interconnected withcommunication links, the interface element comprising: monitor means formonitoring a state of at least two of the communication links coupled tothe interface element; and, dependent on the monitored state of at leastone of the communication links, the monitor means is operative forinforming other network elements of the communication network of changesdetected by the monitor means in the monitored state of at least one ofthe communication links over another of-the communication links coupledto the interface element. 40: The interface element according to claim39, in which the monitor means monitors a state of the network byreceiving at least one message regarding the state of at least one ofthe communication links of the network. 41: The interface elementaccording to claim 40, in which the at least one message comprisesinformation regarding an ability of the at least one communication linkto carry information. 42: The interface element according to claim 40,in which the at least one message is received from at least onelink-state monitor of the interface element. 43: The interface elementaccording to claim 40, in which the at least one message is receivedfrom at least one component of the network. 44: The interface elementaccording to claim 40, in which the at least one communication linkcomprises a peripheral link of the network, the peripheral linkconnecting the network and the interface element. 45: The interfaceelement according to claim 39, in which the monitor means monitors astate of the network by receiving at least one message regarding a stateof at least one component of the network. 46: The interface elementaccording to claim 45, in which the at least one message comprisesinformation regarding an ability of the at least one component to carryinformation. 47: The interface element according to claim 45, in whichthe at least one message is received from the at least one component.48: The interface element according to claim 39, in which the monitormeans monitors a state of the network by receiving at least one messageregarding at least one connection path available to at least onecomponent of the network. 49: The interface element according to claim48, in which the at least one message comprises information regardingconnection paths between the at least one component and at least oneother component of the network and at least one element which interfaceswith the network. 50: The interface element according to claim 48, inwhich the at least one message comprises information regarding a measureof a cost of using the at least one connection path. 51: The interfaceelement according to claim 48, in which the at least one message isreceived from the at least one component of the network. 52: Theinterface element according to claim 39, in which the monitor meansmonitors a state of the network by registering any changes in the stateof the network. 53: The interface element according to claim 52, inwhich the monitor means monitors the state of the network by registeringany changes in the state of at least one of the communication links andat least one component of the network. 54: The interface elementaccording to claim 39, in which the monitor means monitors a state ofthe network by registering any faults occurring in the network. 55: Theinterface element according to claim 39, in which the monitor meanscommunicates with at least one component of the network. 56: Theinterface element according to claim 55, in which the monitor meanscommunicates a state of the network to the at least one component of thenetwork. 57: The interface element according to claim 39, in which themonitor means communicates a state of the interface element to at leastone component of the network. 58: The interface element according toclaim 39, in which the monitor means is operative for monitoring a stateof the network and allows the interface element to react to the state ofthe network. 59: The interface element according to claim 39, in whichthe monitor means is operative for monitoring any changes in a state ofthe network and allows the interface element to compensate for a changein the state of the network. 60: The interface element according toclaim 59, in which the monitor means is operative for compensating for achange in the state of the network by causing information sent by it tothe network to be rerouted. 61: The interface element according to claim60, in which rerouting of the information takes place in sub-secondtimes. 62: The interface element according to claim 60, in which themonitor means provides a routing function. 63: The interface elementaccording to claim 39, in which the monitor means is implemented on atleast one microprocessor added to the interface element. 64: Theinterface element according to claim 39, in which the monitor means isimplemented on at least one existing microprocessor of the interfaceelement. 65: The interface element according to claim 39, in which themonitor means comprises a router. 66: The interface element according toclaim 65, in which the router comprises at least one microprocessorrunning routing protocol software. 67: The interface element accordingto claim 66, in which the routing protocol software comprises routingprotocol software with which at least one component of the networkcommunicates. 68: The interface element according to claim 66, in whichthe routing protocol software comprises the Open Shortest Path First(OSPF) routing protocol. 69: The interface element according to claim39, in which the monitor means connects the interface element to thecommunications network. 70: The interface element according to claim 69,in which the monitor means comprises at least two connections to thecommunications network. 71: The interface element according to claim 39,in which the interface element comprises a host. 72: The interfaceelement according to claim 71, in which the host is one of a media and aresidential gateway programmable device. 73: The interface elementaccording to claim 39, in the communications network is apacket-switched network. 74: The interface element according to claim73, in which the packet-switched network is an internet protocol (IP)based network operating over a link-layer protocol. 75: The interfaceelement according to claim 39, in which the communications networkcarries telephony-type information and data information. 76: A method ofusing an interface element to monitor a state of a communicationsnetwork having network elements interconnected with communication links,comprising the steps of: monitoring a state of at least two of thecommunication links coupled to the interface element; and, dependent onthe monitored state of at least one of the communication links,informing other network elements of the communication network of changesdetected in the monitored state of at least one of the communicationlinks over another of the communication links coupled to the interfaceelement.